SiN etching characteristics of Ar/CH₃F/O₂ plasma and dependence on SiN film density

Abstract

We evaluated the silicon nitride (SiN) etching characteristics of Ar/O2/hydrofluorocarbon plasma. Ar/CH3F/O2 plasma achieved a high etching selectivity of SiN to SiO2 by increasing the oxygen flow rate. We also evaluated the dependence of SiN etching characteristics on SiN film density. A low-density film deposited at a low temperature of 200 °C (by plasma-enhanced CVD, PECVD) showed an 8–20% lower etching rate of SiN than a high-density film deposited at a high temperature of 780 °C (by low-pressure CVD, LPCVD) when we had a low RF bias of 30 W. This PECVD film might move the competitive balance to oxidation from fluorination, reducing the SiN etching rate. However, when we have a high RF bias of more than 50 W, the SiN etching rate is 2–15% higher in the PECVD film than in the LPCVD film. The etching rate of SiN at various densities depends on the balance between oxidation and ion bombardment.

Dry-Etching Processes for High-Aspect-Ratio Features with Sub-10 nm Resolution High-χ Block Copolymers

“…The transfer of the PDMSB/SOC features into SiN was achieved with a Ar/CH 3 F/O 2 gas chemistry (Ar 200 sccm, CH 3 F 70 sccm, O 2 30 sccm, 10 mT, 400 Ws, 50 Wb). Other attempts with an Ar/CF 4 /CHF 3 plasma showed poor selectivity, limiting the depth of the transfer into SiN to approximately 20 nm before complete etching of the SOC mask.…”

“…This is in agreement with previous observations, where the etching conditions should favor sidewall passivation via the deposition of poorly volatile brominated etch products formed during SOC etching. 28 The transfer of the PDMSB/SOC features into SiN was achieved with a Ar/CH 3 F/O 2 gas chemistry 30 (Ar 200 sccm, CH 3 F 70 sccm, O 2 30 sccm, 10 mT, 400 Ws, 50 Wb). Other attempts with an Ar/CF 4 /CHF 3 plasma showed poor selectivity, limiting the depth of the transfer into SiN to approximately 20 nm before complete etching of the SOC mask.…”

Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H2 and CF4/H2 Plasmas

“…It has also been reported that high SiN/SiO 2 selectivity can be achieved using gas mixtures such as NF 3 /O 2 or CF 4 /N 2 /O 2 plasmas, which is attributed to the influence of NO radicals. , The addition of hydrogen to fluorocarbon gas, leading to the generation of CH x F y ions, can be used to enhance the etch rate (ER) and/or selectivity of SiN/SiO 2 or SiN/Si. − Special hydrofluorocarbon gases have been used to achieve high etch selectivity for SiN over SiO 2 and Si. − Additionally, the dependence of selectivities between Si-based materials on substrate temperature has recently been investigated by various research groups. , In hydrogen-contained fluorocarbon plasmas, the formation of hydrogen fluoride (HF) is anticipated to have a detrimental effect on etching for Si-based materials, as it tends to scavenge F radicals . In the mechanism of SiN etching, the H also reacts with N and CF x species, resulting in the formation of HCN as a byproduct, which helps to reduce the FC polymerization and facilitates the progress of SiN etching. , Based on the experimental and simulation results, it has been reported that HF molecules appear to play an important role in the selective etching of SiN over SiO 2 in NF 3 /N 2 /O 2 /H 2 remote plasmas , On the other hand, recently, there have been investigations into the selective etching of SiO 2 over SiN or Si using an HF vaper, employing both computational simulations and experimental approaches. , …”

Gate spacers etching of Si3N4 using cyclic approach for 3D CMOS devices

“…[3][4][5][6] or hydrofluorocarbon C x H y F z (Refs. [7][8][9][10][11][12][13][14][15] chemistries. Fluorine-rich gases such as CF 4 , C 4 F 8 , or CHF 3 with a high Si 3 N 4 etch rate of about 30 nm min −1 were investigated.…”

“…6,9,10,13,17 Oxygen helps to reduce the concentration of fluorocarbon radicals like CF x by forming volatile species such as CO, CO 2 , or COF 2 and enhance Si 3 N 4 etching. 9,10,18 Hydrogen from incident hydrofluorocarbon tends to increase the etching rate of Si 3 N 4 compared to fluorocarbon without hydrogen by the possible reaction of volatile species, such as HCN. 18,19 Moreover, it scavenges fluorine from the deposited film, reducing its fluorine content.…”